Feline urethral obstruction

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Feline urethral obstruction is an unfortunately common affliction in the emergent veterinary patient. Approaches to short- and long-term management vary by the clinician, but the immediate concern is stabilization and relief of the obstruction.

The typical patient is a male neutered cat, with a gender bias on the basis of urethral anatomy. They can present at any age, but environmental stressors (a new housemate, construction in the household, moving, boarding, etc.) often play a role. Overweight cats may also be more prone to lower urinary tract disease.

The history is fairly common among cats with any degree of lower urinary tract disease ranging from sterile cystitis to complete obstruction. Urinary-specific signs include stranguria, hematuria, pollakiuria, and urinating outside the litterbox. More systemic signs including vomiting, lethargy, inappetence, and vocalizing can arise at any point in the process, and if left untreated, can progress to obtundation.

Physical exam reveals a firm, often painful bladder which is not readily expressed. The tip of the penis may be inflamed, and closer examination may reveal a mucus plug or other debris. The size of the bladder may be suggestive of the duration of obstruction but a smaller bladder does not rule out obstruction if other compatible clinical signs are present. Cats will often present with evidence of dehydration and nausea. More severely affected animals may have poor pulses, or show bradycardia secondary to electrolyte disturbances.

The initial database at the point of triage consists primarily of bloodwork to assess electrolytes and renal values. Common findings include azotemia (more post-renal than pre-renal but often both are present), hyperkalemia, and hypocalcemia. With severe hyperkalemia, corresponding ECG abnormalities may be seen. In the interest of efficiency, if a blocked cat is successfully identified at triage, additional diagnostics (urinalysis, urine culture, and abdominal radiographs which include the distal urethra) are typically postponed until the unblocking procedure is complete. Cystocentesis of a blocked cat is typically discouraged in the interest of bladder mucosal health. Abdominal ultrasound can be considered if soft tissue abnormalities (e.g., stricture, neoplasia) are suspected.

In the sick blocked cat, initial stabilization includes IV fluids and treatment of life-threatening arrhythmias. Calcium gluconate is administered for cardiac protection, and insulin/dextrose are given to address significant hyperkalemia (>7mEq/L). In especially sick cats, urethral catheterization can be attempted without sedation to relieve the obstruction as quickly as possible.

In the stable male cat, sedation is typically required prior to catheterization. This aids with patient restraint as well as prevention of urethrospasm. Many strategies exist to achieve relief of the obstruction, but the guiding principle is, as with all of medicine, “first do no harm.” In other words, even in the most challenging urethras, the use of ample lubrication and gentle pressure must be paramount in order to prevent compromise of an already inflamed urethra.

A urine sample is collected during catheterization for urinalysis and culture, as appropriate. An appropriate indwelling urinary catheter is placed and connected to a closed urine collection system for monitoring of outputs and the character of the urine. A placement radiograph aids both in assessing the

urinary catheter placement within the bladder and in evaluating for the presence of cystic calculi or any other abnormalities of the urinary tract. The distal urethra should be included in the radiograph to assess for the presence of urethral calculi.

Depending on the duration of obstruction and the patient’s condition, the urinary catheter is ideally left in place for at least 12-24 hours, and an E-collar is imperative to prevent premature failure of this plan. IV fluids are continued and adjusted as needed to balance against urine output. We frequently see a post-obstructive diuresis in these cats, so fluid status must be watched closely via ins/outs, weights, and clinical assessment. The urinary bladder can be gently flushed to aid in the clearing of sedimentary debris, but care must be taken with excessive flushing which can cause additional bladder inflammation.

In-hospital medications include prazosin, robenacoxib (in the absence of azotemia on presentation), antibiotics (subject to doctor discretion based on the suspect cause of the obstruction and the degree of contamination during unblocking), and pain control. Pending urinalysis results, the patient is typically fed an appropriate diet for management of feline lower urinary tract disease.

After the urinary catheter is pulled, the patient is typically monitored for another 12-24 hours to ensure adequate urinary habits. Although straining and mild discomfort may continue, the cat should be able to pass a reasonable urine stream and empty his bladder when needed.

Discharge instructions review appropriate diet, water availability, stress control, and monitoring of urine output at home. This can often mean separating the cat from housemates and providing his own litter box. Although this may increase stress in the short term, it will help in the identification of any issues in the immediate post-unblocking period.

Unfortunately, urinary obstruction is typically not a one-time experience, and many cats will re-present with either lower urinary tract signs or complete obstruction. Adherence to dietary and medical recommendations at home is key to the management of these cases long term. Although no true cure exists for the cat who is prone to these signs, close observation, and rapid intervention can ensure a normal lifespan with a limited recurrence of the problem.

Submitted by: Dr. Melissa Ogg

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